Sliding closures of this type are known in various configurations. Publication EP 1 119 428 discloses, for example, a sliding closure comprising two fireproof closing plates with a metallic housing that can be fastened to the container and which accommodates the upper closing plate and a fireproof inlet sleeve on the container side. The lower closing or slide plate serving to open and close a spout opening is arranged in a metallic slide unit which additionally accommodates a fireproof spout sleeve adjoining the slide plate.
It is well known that the fireproof parts of the sliding closure, in particular the two closing plates, but also the inlet sleeve on the container side and the spout sleeve adjoining the slide plate such as to form a seal are subjected to a high degree of wear and tear, and so have to be changed regularly.
However, the high temperatures occurring during casting also subject the housing accommodating the inlet sleeve and the upper closing plate as well as the slide unit containing the slide plate and the spout sleeve to a high degree of stress, in particular in the region lying close to the flow-through opening and enclosing the spout sleeve and the inlet sleeve, where the highest temperatures prevail and so the greatest stresses occur. In addition, the sliding closure experiences a high degree of heating from below, and so in particular this slide unit accommodating the spout sleeve is subjected to an extremely high degree of thermal stress.
The same problem also arises with sliding closures which comprise a slide plate that can be displaced between two stationary closing plates (see e.g. EP 0 891 829 A1) in which the housing that can be fastened to the container also accommodates the inlet sleeve as well as the spout sleeve and the casting pipe in addition to the two stationary closing plates.